How do you calculate the number of rotations of a sphere?
In order for us to be able to do the two particular rotations described in the previous paragraph, it is sufficient that the sphere intersects the line given by the pair of equations x = x1, y = y2. The number of intersections with that line gives the number of intersections of the two circles.
What are the angles and positions of the celestial sphere?
The Celestial Sphere, Angles, and Positions The Celestial Sphere, Positions, and Angles Objectives: •Develop a coordinate system •How do you measure distances on a sphere The Celestial Sphere Earth at center of very large sphere Because sphere is so large, observer, is also at center (figure not to scale). Stars in fixed positions on sphere
Which is part of the sphere is inside the circle?
The sphere intersects that plane in a circle that passes through the points (x1, y1, z1) and (x2, y2, z2). At least one of the points (x1, y1, z2) and (x2, y2, z1) lies inside or on that circle, and therefore is inside or on the sphere.
What does declination mean on the celestial sphere?
•Declination (0-90°): The north/south positions of points on the celestial sphere. “Latitude” •Right Ascension (0-24 hrs): The east/west positions of points on the celestial sphere. “Longitude” • These two give the location of any object on the sky Dec=90° Dec=0° Local Horizon Coordinate System Horizon:Where the Ground meets the sky
How is the mass of a spiral galaxy determined?
In either models, observed rotation velocities in spiral galaxies show that the mass in their halos is dominated by dark matter. The mass-to-luminosity (M/L) ratio can be obtained by dividing SMD by surface luminosity profiles ( Forbes 1992 ; Takamiya and Sofue 2000 ; Vogt et al. 2004a ).
Which is the farthest rotation velocity of a spiral galaxy?
4.1.5. Mass-to-luminosity ratio The farthest rotation velocity so far measured for a spiral galaxy is that for the Milky Way and M31 up to ∼ 300 kpc, where the kinematics of satellite galaxies was used to estimate the circular velocities ( Sofue 2012 , 2013b ). The obtained rotation curve was shown to be fitted by the NFW density profile.